Description of Business, Basis of Presentation, and Summary of Significant Accounting Policies - Loans and Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued interest on loans held-for-investment	$ 35	$ 43
Loans receivable, minimum number of days past due to be placed on non-accrual status	90 days
Maximum period for payment deferrals, forbearance and extensions as response to COVID-19	18 months
COVID-19 Pandemic
Financing Receivable, Allowance for Credit Losses
Decrease in reserves	$ 65